DESCRIPTION

Field of the invention

The present invention relates to the field of methods for producing mattresses or the like, more precisely to a method for producing a foam mattress or the like and to a mattress or the like thus obtained.

Background art

Known foam mattresses have been in use for years due to their high performance especially in terms of load-carrying capacity, as well as for their good durability. In the case of latex foam, for example, the mattress typically consists of a solid latex part having a predetermined density, in which through or non-through holes (alveoli) are then made. The mattress may be either one piece or made up of distinct modules, which are joined together by using various techniques.

Production processes for latex mattresses are substantially known, among which, for example, those called "Dunlop" and "Talalay"; methods for producing polyurethane mattresses are known as well.

Several attempts have been made to improve such products for increased user comfort. Materials of the type known as "PCM", which stands for "phase change materials", are known to be inserted into mattresses, for example as described in patent US2009288259A1. Said materials have the property of changing their phase (from solid to liquid and vice versa) according to the external temperature they are subject to. During the phase change, they absorb and then release a considerable quantity of energy or heat, with different behavior in the respective absorption and release stages. While absorbing heat in contact with a source of energy, e.g. due to a temperature increase, thus switching from the solid phase to the liquid phase, a PCM tends to not increase its temperature for quite a long time, because the energy introduced therein is absorbed in order to generate the phase change; on the contrary, the release of energy and the return to the solid phase tends to be fast.

In a mattress or the like, the addition of said material tends to increase the comfort of the person lying on it, in that the energy released by his/her body will not cause an immediate increase in the temperature of the mattress, which on the contrary will tend to stay cool for some time.

However, the use of said materials is not without drawbacks, which are substantially due to the fact that the person can hardly perceive the advantages deriving from the positive temperature behavior of the mattress, since the phase change resulting from the temperature variation is not evident to him/her.

Moreover, this difficulty of perception leads to further problems when designing the mattress, especially as regards the choice of the most appropriate quantities and type of PCM product to be used.

When PCM is present, the thermal change behavior is different between latex and paraffin, and therefore there is a need for providing a system for highlighting the thermal behavior thereof in order to obtain an evaluation system based on which one can choose the product that best meets his/her requirements. This must be applicable to both conditions of temperature increase and heat release to return to the initial condition. It is therefore also important to consider the stage in which the initial condition is returned to, in the sense that warming up must occur as delayed as possible, whereas the return to the initial condition must be quick.

Summary of the invention

It is therefore the object of the present invention to provide a method for producing a foam mattress or the like, and a mattress or the like thus obtained, which are adapted to solve the above-mentioned problems.

In accordance with the main aspects of the present invention, it has been found out that the presence of thermo-chromic pigments or compounds thereof, with various types of behaviors in terms of chromatic variations as a function of temperature, and the simultaneous use of PCM allow the map of the thermal behavior at the interface between the human body and the foam mattress or the like to be evaluated also over time, for the purpose of obtaining improved comfort, product customization and thermoregulation. This should take into account both the different temperatures developed by the human body, when placed in contact with the foam, and the different stages in the course of the expected life of the mattress, as well as the different pressures exerted by the body in different postures on different areas of the mattress or the like.

It is a particular object of the present invention to provide a method for producing a foam mattress or the like, characterized in that it comprises the steps of: preparing the basic components of the foam of the mattress or the like; preparing a compound of a first quantity of phase change material (PCM), which is adapted to change its phase as a function of temperature, and a second quantity of thermo-chromic or thermo-sensitive pigment (TP), which is adapted to change its color as a function of temperature; producing said mattress or the like by using said basic components and said compound. According to a first variant of the method, said compound is added to said basic components during the production of the mattress or the like, in the whole mattress or the like or in a part thereof.

According to a second variant of the method, said compound is applied to the outer surface of the mattress or the like after the mattress or the like has been produced with said basic components, throughout said outer surface or on a part thereof.

It is a further object of the present invention to provide a mattress, or a pillow, an armchair, a sofa or a sofa-bed, or parts thereof, obtained by using said method.

It is a particular object of the present invention to provide a method for producing foam mattresses or the like, as well as a mattress or the like thus obtained, as set out in the claims, which are an integral part of the present description.

Brief description of the drawings

Further objects and advantages of the present invention will become apparent from the following detailed description of an example of embodiment (and variants) thereof and from the annexed drawings, which are only supplied by way of non-limiting example, wherein:

Figures 1 to 4 show different graphs of the color variation C occurring in the foam mattress or the like as a function of temperature T;

Figures 5 and 6 show some examples of devices used for implementing the second variant of the method, in particular a spray airbrush and a drying oven, respectively.

In the drawings, the same reference numerals and letters identify the same items or components.

Detailed description of embodiments of the invention

Thermo-chromic or thermo-sensitive pigments TP are a per se known type of material that comprises thermo-sensitive substances having the property of changing their color (losing or gaining color) as a function of temperature in a reversible manner, such substances being normally enclosed in water-insoluble spherical capsules in the form of dispersion or powder. Typically, the diameter of the microcapsules is 1-30 micron.

When said pigments reach a so-called "color change temperature" interval, represented as the interval TO - Tl in the figures, they begin to change their color. The color change temperature is typical of the pigment: for example, pigments are known which have a color change temperature between -15°C and 65°C.

For use in a mattress or the like, it is preferable that the color change temperature of the thermo-chromic or thermo-sensitive material is, for example, 28 °C, i.e. close to average body temperature.

Thermo-chromic or thermo-sensitive pigments TP may have several types of behavior in terms of chromatic variations as a function of temperature, for example:

- in a first type (Fig. 1), under the color change temperature the pigment is colored in a saturated manner, whereas at the color change temperature it starts a loss of color process that leads it, above the color change temperature, to become colorless;

- in a second type (Fig. 2), the opposite phenomenon occurs;

- in a third type (Fig. 3), the color variation is also dependent on the temperature gradient, and follows different paths during the two stages of temperature increase and decrease.

- in un fourth type (Fig. 4), within the change color temperature interval the pigment is colored, whereas outside said interval it loses color and becomes colorless.

There is also a further type that changes color also as a function of pressure, in addition to temperature: at a normal pressure (approx. 1 bar) the pigment is colorless, whereas as pressure increases it gains color; as far as temperature is concerned, it behaves like the first type.

It is possible to obtain compounds of different types of thermo-chromic or thermo- sensitive pigments TP having different chromatic hues, and they can be mixed with normal non-thermo-chromic pigments, like those already in use for traditional coloring of a mattress or the like, thus attaining chromatic effects of various nature. For example, it is possible to have either only the color of the thermo-chromic or thermo-sensitive pigment TP or only the traditional color appear at normal temperature, the other color appearing as temperature increases, or vice versa.

In the mattress or the like, thermal conditioning is created by the PCM material, which in practice is a type of high-density paraffin, preferably contained in the form of powder or dispersion in microcapsules or microspheres, the diameter of which may vary, for example, between 3 and 15 micron.

Different types of PCM's are available on the market, which are also characterized, among other things, by the temperature around which the phase change occurs, also known as "color change temperature" or "melting point".

For use in a mattress or the like, it is preferable that the color change temperature of the PCM is, for example, 28 °C, i.e. close to average body temperature, which is a good compromise between room temperature and body temperature.

In accordance with a first variant of the method of the present invention, during the process of producing a mattress or the like, a suitable compound of given quantities of phase change materials (PCM) and of a type of component materials known as thermo- chromic or thermo-sensitive pigments (TP) is added to the basic foam components.

Therefore, during the process of producing the mattress of the like, a liquid compound is prepared starting from latex, and the compound of PCM and TP in dispersion or powder is then added.

The following will describe in detail one example of embodiment of the first variant of the production method by using latex, which may be of a known type, whether natural or synthetic, wherein the compound is subjected to mechanical foaming, followed by gelling with sodium fluosilicate and steam curing at 100° C for approx. 30 minutes in the mold. A closed mold may be used, into which latex is injected according to a substantially known process, e.g. "Dunlop" or "Talalay".

The mold may contain inner protuberances suitably shaped for obtaining the empty parts (alveoli) of the mattress.

Phase Change Materials (PCM) and Thermo-chromic Pigments (TP) are added to the latex foam, thus obtaining the desired compound.

For example, for a compound obtained with the Dunlop process, the following steps are carried out:

1 . Preparation of PCM dispersion

- 1000 g water

- 500 g Lurapret® TX PCM 28

- 10 g potassium resinate

- 40 g CMC

- Fast stirring for 5 min

2 . Preparation of TP dispersion:

- 500 g TP

- 50 g water - Fast stirring for 5 min

- Note: TP's may be either homogeneous or a mixture of TP's with different characteristics; they are available on the market, and in this case those with a color change temperature of approx. 28°C are used.

3 . The PCM and TP dispersions are mixed and subjected to fast stirring for 5 min in order to homogenize them.

4 . The dispersion obtained at step 3 is mixed with the latex compound in a quantity between 5% and 15% of the compound.

The above-described process may even be applied to a part of the mattress only, e.g. by dividing the latter into layers in the thickness direction and by applying the PCM and TP to one or two lateral layers.

Normal, fixed-color pigments may be coupled at will with TP's in order to obtain the desired gradation.

It can therefore be achieved that, de facto, at high temperature only the normal pigment is visible because the TP becomes transparent, whereas only the TP can be seen at low temperature.

In accordance with a second variant of the method of the present invention, a known process for producing a mattress or the like with basic foam components (latex or polyurethane) is first implemented, so as to obtain a foam mattress of the traditional type. This is followed by a step of applying onto the mattress a surface layer comprising a compound of PCM and TP components.

The surface layer may be applied by spraying or by immersion in a suitable bath.

The application may concern the whole surface of the mattress or only a part thereof, e.g. a major side where contact with the body occurs.

The following will describe in detail one example of embodiment of the second variant of the production method.

The mattress, e.g. a latex one, is first produced as described above for the first variant by using latex, which may be of a known type, whether natural or synthetic. According to the method, the compound is then subjected to mechanical foaming, followed by gelling with sodium fluosilicate and steam curing at 100° C for approx. 30 minutes in the mold. A closed mold may be used, into which latex is injected according to a substantially known process, e.g. "Dunlop" or "Talalay". The mold may contain inner protuberances suitably shaped for obtaining the empty parts (alveoli) of the mattress. After having obtained the mattress or the like, the second step is carried out, wherein the surface layer comprising the compound of PCM and TP components is applied.

For spray application, the PCM and TP components are applied by using a latex-based colloidal dispersion with gluing properties.

Preferably this is followed by a drying step.

For example, the following steps are carried out for spray application on a normally sized mattress:

1. Preparation of a dispersion of TP material consisting of:

320 g TP powder;

520 g water.

2. Preparation of a dispersion of PCM material consisting of:

100 g PCM powder;

200 g water.

3. Preparation of total dispersion:

300 g polychloroprene latex;

60 g TP dispersion;

60 g PCM dispersion.

The final compound is applied by spraying, e.g. by using an airbrush 51 (Fig. 5), which is passed across the surface of the mattress 52. The airbrush has a series of spray nozzles 53 which spray the total dispersion, preferably at room temperature, with compressed air. The movement of the airbrush is normally controlled at constant speed, so that the dispersion can be applied evenly onto the mattress surface; however, application may also be uneven. The dispersion to be applied may be contained in a suitable tank connected to the airbrush.

Instead of using an airbrush, spraying may also be done manually.

A drying step is then preferably carried out, e.g. by air, UV radiation or infrared radiation. The mattress is conveyed into a suitable drying oven 61 (Fig. 6), preferably of the non-ventilated type to avoid dispersion detachment phenomena, at a temperature that may be higher than room temperature, for a shorter drying time, or at room temperature. Optionally, a further step of applying superimposed text or illustrations onto the surface of the mattress or the like may be carried out for a possible customization thereof.

Application is done by spraying through the use of ^" preformed masks as contours, according to two possible variants: - after the main spraying, spraying of thermo-chromic material in a different specific quantity for the same area compared to the main spraying, in particular a larger quantity, possibly in a different color shade,

or

- before the main spraying, spraying of non-thermo-chromic material directly onto the mattress.

Therefore, as contact temperature increases, the thermo-chromic material will become transparent, thereby highlighting the superimposed or underlying text or illustrations, which may have an evident color, whereas at room temperature the thermo-chromic layer will hide the superimposed or underlying text or illustrations.

As mentioned above, the main spraying may be replaced by immersion of the mattress in a suitable bath containing the above-described substances.

The method for producing a latex mattress in the above-described variants is also applicable to pillows and other types of goods, such as, for example, paddings of armchairs, sofas or sofa-beds.

The advantages of the present invention are apparent.

A simple and effective system for increasing the performance of the mattress or the like is thus obtained, in that the user can more easily perceive the thermal effect, and the design of the mattress or the like is also improved.

From the above description, those skilled in the art will be able to produce the object of the invention without introducing any further details.

In particular, known machinery and devices can be used for the production of both the semi-finished products and the finished product.

The elements and features shown in the various preferred embodiments may be combined without however departing from the protection scope of the present invention.